Bis-(hydroxyalkylamino)-anthraquinone inhibitors of protein kinase C

ABSTRACT

The present invention provides novel substituted anthraquinones having the formula ##STR1## wherein R 1  and R 2  are independently H, C 1  -C 10  alkyl, aryl, arylalkyl, alkylaryl; 
     n and m are independently 1, 2, or 3; 
     A is Halogen, OH, alkoxy, OCO(NR 3  R 4 ), S--C(NH 2 )═NR 5 , or when m=1, comprises an oxirane ring with the adjacent oxygen atom; 
     R 3 , R 4 , and R 5  are independently H, alkyl, or aryl; 
     X is H, OH, NR 6  R 7 , Cl, Br, I, F, alkyl, aryl, alkoxy, aryloxy, COOR 8 , or CONR 9  R 10  ; and 
     R 6 , R 7 , R 8 , R 9 , and R 10  are independently H, lower alkyl, or aryl 
     useful for inhibiting protein kinase C and treating conditions related to, or affected by inhibition of protein kinase C, particularly cancer tumors, inflammatory disease, reperfusion injury, and cardiac dysfunctions related to reperfusion injury.

FIELD OF THE INVENTION

The present invention relates to the field of treatments for inflammatory and cardiovascular diseases, and chemotherapeutic agents. More particularly, the present invention relates to novel asymmetric 1,4-bis-(amino-hydroxylalkylamino)-anthraquinones for inhibiting the enzyme protein kinase C.

BACKGROUND OF THE INVENTION

Protein kinase C (PKC) is a family of calcium stimulatable and phospholipid-dependent serine/threonine-specific protein kinases which play an important role in cellular growth control, regulation, and differentiation. protein kinase C is also fundamental to the processes involved in tumorigenicity, since it is the major high-affinity receptor for several classes tumor promoters as well as for endogenous cellular diacylglycerols. These tumor promoters also stimulate protein kinase C catalysis. Castagna et al. (1982) J. Biol. Chem. 257: 7847 reported direct activation of protein kinase C by tumor-promoting phorbol esters. The mechanisms of protein kinase C action have been described in U.S. Pat. No. 4,816,450 issued Mar. 28, 1989 to Bell et al., the disclosures of which are specifically incorporated as if fully set forth herein. protein kinase C is activated by diacylglycerol (DAG), a neutral lipid, and when activated will transfer the γ-phosphate of MgATP to a serine or threonine residue on a substrate protein.

Since the activation of protein kinase C have been implicated in several human disease processes, including cancer tumors, inflammation, and reperfusion injury, inhibition of protein kinase C should be of great therapeutic value in treating these conditions.

Protein kinase C inhibitors have been reported to potentiate the antitumor activity of cis-platin both in vitro and in vivo (Grunicke et al. (1989) Adv. Enzyme Regul. 28: 201; and German Offenlegungsschrift DE 3827974). In addition, it has been suggested that protein kinase C would be a potential target for therapeutic design because of its central role in cell growth (Tritton, T. R. and Hickman, J. A. Cancer Cells 2: 95-102 (1990)).

Protein kinase C inhibitors have been demonstrated to block platelet aggregation and release of neutrophil activating agents such as platelet activating factor (PAF)(Schachtele et al. (1988) Biochem. Biophy. Res. Commun. 151: 542; Hannun et al. (1987) J. Biol. Chem. 262: 13620; Yamada et al. (1988) Biochem. Pharmacol. 37: 1161). protein kinase C inhibitors have also been shown to inhibit neutrophil activation, and chemotactic migration (McIntyre et al. (1987) J. Biol Chem. 262: 15730; Lambreth et al. (1988) J. Biol. Chem. 263: 3818; Pittet et al. (1987) J. Biol. Chem. 262: 10072; and Gaudry et al. (1988) Immunology 63: 715), as well as neutrophil degranulation and release of proteolytic enzymes and reactive oxygen intermediates (Wilson et al. (1986) J. Biol. Chem. 261: 12616; Fujita et al. (1986) Biochem. Pharmacol. 35: 4555; Berkow et al. (1987) J. Leukoc., Biol. 41: 441; Salzer et al. (1987) Biochem. Biophys. Res. Commun. 148: 747; Kramer et al. (1989) J. Biol. Chem. 262: 5876; and Dewald et al. (1989) Biochem. J. 264: 879). Thus inhibitors of protein kinase C have the capability of blocking all three of the most significant mechanisms of pathogenesis associated with myocardial reperfusion injury, and should thus have a decided therapeutic advantage. Additionally, the inhibitory effect of protein kinase C inhibitors on keratinocytes, and on the oxidative burst in neutrophils will lead to an anti-inflammatory effect.

Substituted anthraquinones have been reported for various uses, including cancer treatment. U.S. Pat. No. 3,960,751 issued Jun. 1, 1976 to Moriyama et al. discloses substituted anthraquinones useful as pleochroic dyes. U.S. Pat. No. 4,598,155 issued Jul. 1, 1986 to Adam discloses tetrazole substituted anthraquinones useful as dyes.

U.S. Pat. No. 4,762,648 issued Aug. 9, 1988 to Stache et al. discloses mono-functional and bis-functional anthraquinone-(oxy-2,3-oxidopropanes) useful as intermediates in the preparation of drugs possessing β-receptor blocker action and as crosslinking agents in the preparation of polymers. The compounds also exhibit cytostatic activity.

Several patents disclose the use of substituted anthraquinones for treatment of neoplasms. U.S. Pat. No. 4,894,451 issued Jan. 16, 1990 to Krapcho et al. discloses unsymmetrical 1,4-bis-(aminoalkylamino)anthracene-9,10-diones useful in the treatment of neoplasms. U.S. Pat. No. 4,310,666 issued Jan. 12, 1982 to Zee-Cheng et al discloses 1,4-bis-(substituted aminoalkylamino)-anthraquinones useful in the treatment of neoplasms. U.S. Pat. No. 4,526,989 issued Jul. 2, 1985 to Murdock et al discloses symmetrical 1,4-bis(substituted-amino)- 5,8-dihydroxyanthraquinones useful as chelating agents and for inhibiting the growth of tumors. U.S. Pat. No. 4,197,249 issued Apr. 8, 1980 to Murdock et al also discloses symmetrical 1,4-bis(substituted-amino)-5,8-dihydroxyanthraquinones useful as chelating agents and for inhibiting the growth of tumors. U.S. Pat. No. 4,540,788 issued Sep. 10, 1985 to Murdock discloses 1,4-bis[-aminoalkyl)amino]-9,10-anthracenediones and leuco bases thereof which are useful as chelating agents and for inducing regression of leukemia and/or inhibition of tumor growth in mammals. Japanese patent 19819 issued May 7, 1990 discloses substituted anthraquinones having substituents at positions 5 and 6 of the anthraquinone ring structure which are useful as anti-tumor agents alone or in combination with other anti-tumor agents.

German Offenlegungsschrift DE 3827974 Al discloses therapeutic preparations comprising a protein kinase C inhibitor in combination with a lipid, a lipid analogue, a cytostatic agent or phospholipase inhibitor useful for cancer therapy. However, none of the protein kinase c inhibitors disclosed in this publication are substituted anthraquinones.

Although substituted anthraquinones have been reported for cancer treatments, substituted anthraquinones such as Mitoxantrone, are known to be associated with side effects, mainly immunosuppressive activity, and drug resistance. Accordingly novel cancer treatments that avoid some or all of these drawbacks are needed.

Further, inflammation and reperfusion injury, particularly pertaining to cardiac injury, are common conditions for which there exists no definitive treatment despite extensive research and appropriate treatments for these conditions are needed.

SUMMARY OF THE INVENTION

The present invention provides novel asymmetric substituted anthraquinones having the formula ##STR2## wherein R₁ and R₂ are independently H, C₁ -C₁₀ alkyl, aryl, arylalkyl, alkylaryl, or R₁ and R₂ taken together with the adjacent nitrogen atom N form a substituted or unsubstituted cyclic ring, which ring may optionally contain additional heteroatoms including oxygen, nitrogen or sulphur;

n and m are independently 1, 2, or 3;

A is Halogen, OH, alkoxy, OCO(NR₃ R₄), S--C(NH₂)═NR₅, or when m=1, comprises an oxirane ring with the adjacent oxygen atom;

R₃, R₄, and R₅ are independently H, alkyl, or aryl;

X is H, OH NR₆ R₇, Cl, Br, I, F, alkyl, aryl, alkoxy, aryloxy, COOR₈, or CONR₉ R₁₀ ; and

R₆, R₇, R₈, R₉, and R₁₀ are independently H, lower alkyl, or aryl.

The novel compounds of the invention are useful for inhibiting protein kinase C and are further useful for treating conditions related to, or affected by inhibition of protein kinase C, particularly cancer tumors, inflammatory disease, myocardial reperfusion injury, and cardiac dysfunctions related to reperfusion injury. Inhibition of protein kinase C can lead to inhibition of growth of cells and can thereby produce an anti-tumor effect. Further, inhibition of protein kinase C can also lead to inhibition of the oxidative burst in neutrophils, platelet aggregation, and keratinocyte proliferation, whereby an anti-inflammatory effect is achieved. The inhibitory activities of the compounds of the invention against platelet aggregation, neutrophil activation, and neutrophil release demonstrate their usefulness in treating reperfusion injury, particularly myocardial reperfusion injury.

The compounds of the invention are expected to be particularly useful in the treatment of tumors resistant to treatment with other chemotherapeutic agents. Surprisingly, compounds of the invention are able to inhibit protein kinase C even in adriamycin or Mitoxantrone resistant cells, and thus are not cross-resistant with these chemotherapy agents.

Compounds of the invention are able to inhibit proliferation of tumor cells at low concentrations (less than 1 μM) which should lessen then potential for deleterious side effects of compounds of the invention when administered for treatment of tumors.

The compounds of the invention appear to have no effect on cAMP dependent protein kinase C and should consequently have no effect on the metabolic pathways associated with stimulation of protein kinase C by cAMP.

This invention is more particularly pointed out in the appended claims and is described in its preferred embodiments in the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the synthetic route of Scheme I which is used for synthesis of compounds of the invention.

FIG. 2 shows the synthetic route of Scheme II which is used for synthesis of compounds of the invention.

FIG. 3 shows the synthetic route of Scheme III which is used for synthesis of compounds of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides novel substituted anthraquinones having Formula I ##STR3##

R₁ and R₂ are preferably independently H, C₁ -C₁₀ alkyl, aryl, arylalkyl, alkylaryl, or R₁ and R₂ taken together with the adjacent nitrogen atom N form a substituted or unsubstituted cyclic ring; more preferably H or lower alkyl; most preferably lower alkyl. m and n are preferably independently 1, 2, or 3; more preferably 1 or 2; most preferably 1. A is preferably halogen, OH, alkoxy, OCO(NR₃ R₄), S--C(NH₂)═NR₅, or when m=1, comprises an oxirane ring with the adjacent oxygen atom; more preferably halogen, OCO(NR₃ R₄), SC(NH₂)═NR₅, or when m=1, comprises an oxirane ring with the adjacent oxygen atom; most preferably Cl, Br, OCO(NR₃ R₄), SC(NH₂)═NR₅ or when m=1, comprises an oxirane ring with the adjacent oxygen atom. Halogen as used herein includes fluorine, chlorine, bromine, and iodine. R₃, R₄, and R₅ are preferably independently H, alkyl, or aryl; more preferably H or alkyl; most preferably H. X is preferably H, OH NR₆ R₇, Cl, Br, I, F, alkyl, aryl, alkoxy, aryloxy, COOR₈, or CONR₉ R₁₀ ; more preferably H, HO, Cl, Br, I, F, or alkoxy; most preferably H or OH. R₆, R₇, R₇, R₉, and R₁₀ are independently H, lower alkyl, or aryl. As used herein, the term lower alkyl is intended to mean C₁ -C₆ alkyl.

As used herein, alkyl substituents include straight chain, branched and cyclic moieties, preferably straight chain species. While saturated species are preferred, unsaturated sites may find utility in some substituents. Alkaryl substituents are preferably substituted benzene moieties, with ortho, meta, and para substituents each believed to be useful. Multiple substitutions are similarly useful. Aralkyl substituents are preferably benzene substituted alkanes including benzyl, phenylethyl, phenylpropyl, etc.

The compounds of the invention are useful for treating conditions related to, or affected by inhibition of protein kinase C, particularly cancer tumors, inflammatory disease, reperfusion injury, and cardiac dysfunctions related to reperfusion injury. Accordingly, another aspect of the invention provides methods and pharmaceutical compositions for inhibiting protein kinase C which comprise contacting protein kinase C with an inhibitory amount of a substituted anthraquinone compound of the invention. The pharmaceutical compositions of the invention comprise a substituted anthraquinone compound of the invention and a pharmaceutically acceptable carrier of diluent.

The invention also provides methods of inhibiting an oxidative burst in neutrophils which comprise contacting a neutrophil with a protein kinase C inhibitory concentration of a substituted anthraquinone compound of the invention, or contacting the neutrophil with an amount of a compound of the invention effective to inhibit such oxidative outburst.

The invention further provides methods for treating inflammation which comprise administering to a mammal suffering from inflammation a protein kinase C inhibitory concentration of a substituted anthraquinone compound of the invention, or administering to the mammal an amount of a compound of the invention effective to inhibit inflammation.

The invention additionally provides methods for inhibiting growth of mammalian tumor cells which comprises contacting a mammalian tumor cell with a protein kinase C inhibitory concentration of a substituted anthraquinone compound of the invention, or contacting the tumor cell with an amount of a compound of the invention effective to inhibit growth of the tumor cell.

An additional embodiment of the invention provides methods for treating mammalian tumors which comprise administering to a mammal having a tumor a protein kinase C inhibitory concentration of a substituted anthraquinone compound of the invention, or administering to the mammal having a tumor an amount of a compound of the invention effective to inhibit growth of the tumor.

Another embodiment of the invention provides methods of inhibiting mammalian keratinocyte proliferation which comprises administering to a mammalian keratinocyte a protein kinase C inhibitory amount of a compound of the invention, or administering to the keratinocyte an amount of a compound of the invention effective to inhibit proliferation of the keratinocyte.

Surprisingly, the compounds of the invention are not cross-resistant to adriamycin (Doxorubicin HCl, Adria Laboratories, Dublin, Ohio, an antibiotic-derived chemotherapy agent) or Mitoxantrone (NovantroneN, Lederle Laboratories, Pearl River, N.Y., a synthetic anthracene dione chemotherapy agent), and remain effective in reducing growth of tumor cells resistant to these well-known chemotherapy agents. The lack of cross-resistance with adriamycin or Mitoxantrone indicates that the compounds of the invention will be particularly useful for treatment of adriamycin or Mitoxantrone resistant tumors.

Cancer is a disease characterized in part by uncontrolled cell growth. Protein kinase C is directly involved in cellular growth control and is believed to be involved in tumor formation. Protein kinase C is the major, if not exclusive, intracellular receptor of phorbol esters which are very potent tumor promoters. Phorbol esters and other tumor promoters bind to and activate protein kinase C. Since diacylglycerol (DAG) and phorbol esters interact at the sane site, DAG's have been suggested to be the "endogenous phorbol esters" by analogy with the opiate receptor where the conservation of a high affinity receptor implied the existence of an endogenous analogue. DAG has been shown to increase the affinity of protein kinase C for Ca⁺² and phospholipid and thus activates protein kinase C at cellular levels of these essential cofactors. Extracellular signals including hormones, growth factors, and neurotransmitters are known to stimulate phosphatidylinositol turnover resulting in the generation of IP₃ and DAG. Structures of 40 distinct oncogenes of viral and cellular origin have revealed that oncogenes encode altered forms of normal cellular proteins. Several of the gene products appear related to growth factors or other elements involved in transmembrane signalling. These oncogene products appear to function by altering the level of critical second messengers. Cells transformed with the oncogenes ras, sis, erbB, abl, and src have been shown to contain elevated levels of DAG which is then believed to activate protein kinase C. Indeed studies on ras transformed cells have shown protein kinase C activation to concomitant with elevation of DAG.

Phorbol esters, such as phorbol myristate acetate (PMA), have complex effects on cells including effects on membrane function, mitogenesis, differentiation, and gene expression. Synthetic diacylglycerols mimic many of the effects of PMA in vitro and inhibitors of protein kinase C have been shown to block PMA-induced effects on cells. Thus, protein kinase C may mediate the actions of certain oncogenes, such as ras, which cause intracellular increases in DAG and concomitant increases in protein kinase C. In addition, activation of protein kinase C leads to the expression of c-myc, c-fos, c-cis, c-fms, nuclear protooncogenes important in cell transformation. Overexpression of protein kinase C in NIH 3T3 cells causes altered growth regulation and enhanced tumorigenicity and in rat fibroblasts leads to anchorage-independent growth in soft agar. In these experiments, overexpression of protein kinase C in these cells resulted in tumor formation in animals receiving transplanted cells.

Several studies have shown increased expression of protein kinase C in certain tumor types such as breast and lung carcinomas. Activated protein kinase C has also been detected in human colon carcinomas although increased expression on the gene level was not seen. Topoisomerases are directly modulated by protein kinase C as substrates for the enzyme and protein kinase C inhibitors have been shown to potentiate the action of chemotherapy drugs such as cis-platinum.

New and more potent compounds which have been identified specifically as inhibitors of protein kinase C are showing early promise as therapeutic agents in inhibiting tumor growth in animal models.

Animal studies have shown that perhaps 50% or more of ischemic-related myocardial damages can be attributed to polymorphonuclear leukocytes (neutrophils) which accumulate at the site of occlusion. Damage from the accumulated neutrophils may be due to the release of proteolytic enzymes from the activated neutrophils or the release of reactive oxygen intermediates (ROI). Much of the "no reflow" phenomenon associated with myocardial ischemia is attributed to myocardial capillary plugging. The plugging of capillaries has been attributed to both aggregated platelets and aggregated neutrophils. Although both cell types are aggregated during the ischemic event, the relative contribution of each to capillary plugging has not yet been established. It is well accepted that the damage by neutrophils to myocardial tissue proceeds through a cascade of events, one of the earliest being the bonding of activated neutrophils to damaged vascular endothelium. However, the binding of the neutrophils is significantly enhanced by their activation and this an even earlier event is the generation of molecules (such as cytokines, and chemotactic factors) which can function as activation stimuli. These molecules probably originate from damaged and aggregated platelets, from damaged vascular endothelium, or from the oxidation of plasma proteins or lipids by endothelial-derived oxidants.

Strategies for overcoming the deleterious effects of reactive oxygen intermediates have centered in the development of scavengers for the molecules. Superoxide dismutase (SOD) has been shown to be a particularly effective scavenger of superoxide, but suffers from a very short half-life in the blood. Several companies have tackled this problem by creating versions of this enzyme with increased half-lives by techniques such as liposome encapsulation or polyethylene glycol conjugation. Reports on the effectiveness of these new version are mixed. Catalase, a scavenger of hydrogen peroxide, and hydroxyl radical scavengers have also been tested and found to be effective to varying degrees. However, none of the strategies designed to scavenge reactive oxygen intermediates will prevent the aggregation of platelets, the release of chemotactic molecules, the activation and adherence of neutrophils to vascular endothelium, or the release of proteolytic enzymes from activated neutrophils.

The advantage of protein kinase C inhibitors as therapeutics for reperfusion injury is that they have been demonstrated to 1)block platelet aggregation and release of neutrophil activating agents such as PAF, 2) clock neutrophil activation, chemotactic migration, and adherence to activated or damaged endothelium, and 3) block neutrophil release of proteolytic enzymes and reactive oxygen intermediates. Thus these agents have the capability of blocking all three of the most significant mechanisms of pathogenesis associated with reperfusion injury and should thus have a decided therapeutic advantage.

The compounds of the invention may be made according to the methods in Scheme I, II and III, as shown in FIGS. 1, 2 and 3, respectively. Other synthetic routes known in the art may also be used. As used herein, the anthraquinone ring structure has the conventional ring numbering as illustrated in the Merck Index, Tenth Edition, Merck & Co., Inc. Rahway, N.J., 1983, pp.100-101.

When A is halo or comprises an oxirane ring with the adjacent oxygen atom, the compounds of the invention may be prepared according to the method in Scheme I shown in FIG. 1. In Scheme I, reaction of diaminoanthraquinone 1 with epihalohydrin produces bis-(3-halo-2-hydroxypropylamino)-anthraquinone 2 which upon treatment with amine, such as diethylamine, at temperatures from room temperature to the boiling temperature of the chosen solvent, yields the product Ia. The epoxide analog Ib was obtained by treating Ia with base such as sodium hydroxide. An alternative procedure, shown in Scheme II in FIG. 2, is the conversion of the bis-halohydrin intermediate 2 via basic treatment to bis-epoxide 3 followed by reaction of 3 with amine to yield Ib. Examples of compounds which may be prepared according to Schemes I and II are listed in Tables 1 and 2.

When A is a functional group other than halo or comprising an oxirane ring with the adjacent oxygen, the compounds of the invention listed in Table 1 may be prepared according to Scheme III as shown in FIG. 3. For example, as shown in FIG. 3, compound Ia from Scheme I is converted from the halo compound to the hydroxy compound Ic. The hydroxy compound is then used for the synthesis of compounds having the formula of I wherein A is alkoxy, OCO (N₃ R₄) or SC (NH₂ ═NR₅ using the method disclosed in Kocovsky et al. (1986) Tetrahedron Letters 27: 5521, the disclosures of which are hereby incorporated by reference as if fully set forth herein. Other methods known in the art are also suitable for the synthesis of compounds of the invention.

The optically active enantiomers of the compounds of the invention can be prepared according to Schemes 1 and 2, using optically active starting materials such as the commercially available glycidol or epichlorohydrin.

Pharmaceutically acceptable salts of the compounds of the invention are also useful in the methods of the invention. Pharmaceutically acceptable salts useful in the invention include salts of hydrochloric acid, hydrobromic acid, fumaric acid, oxalic acid, malic acid, succinic acid, pamoic acid, sulfuric acid and phosphoric acid.

                                      TABLE 1                                      __________________________________________________________________________     Compound                                                                             R.sup.1                                                                            R.sup.2                                                                            X    A        m n MP (°)C.)                               __________________________________________________________________________     1a-1  Et  Et  H    Cl       1 1 106-108 (HCl)                                  1a-2  H   Pr  H    C1       1 1 Hyg                                            1a-3  H   CH.sub.2 Ph                                                                        H    Cl       1 1 Hyg                                            1a-4  Octyl                                                                              Octyl                                                                              5-Cl Br                                                          1a-5  Et  Ph  6-Ph-O                                                                              I        2 3                                                1c-1  Et  Et  H    OH       1 1 Hyg                                            1d-1  Et  Et  H    OCH.sub.3                                                                               1 1                                                1d-2  Me  Et  7-HO O-(n-Bu) 2 2                                                1e-1  Et  Et  H    O.sub.2 CNH.sub.2                                                                       1 1                                                1e-2  Me  Me  8-Br O.sub.2 CNPr.sub.2                                                                      1 2                                                1f-1  Et  Et  H    SC(NH.sub.2)═NH.sub.2                                                               1 1                                                1f-2  n-Bu                                                                               n-Bu                                                                               F    SC(NH.sub.2)═NMe.sub.2                                                              3 3                                                1f-3  n-Bu                                                                               Me  5-COOH                                                                              C(NH.sub.2)═NPr.sub.2                                                               1 2                                                __________________________________________________________________________      (Abbreviations used in Tables 1 and 2:                                         Me  methyl;                                                                    Et  ethyl;                                                                     Pr  propyl;                                                                    Ph  phenyl;                                                                    Bu  butyl;                                                                     Hyg  hygroscopic)                                                        

                  TABLE 2                                                          ______________________________________                                         Compound R.sup.1 R.sup.2 X       m   n   MP (°C.)                       ______________________________________                                         1b-1     Et      Et      H       1   1   98 (d)                                1b-2     H       Pr      H       1   1                                         1b-3     n-Bu    n-Bu    5-HO    2   1                                         1b-4     Pr      Me      5-Br    2   2                                         1b-5     H       H       7-COOH  3   2                                         1b-6     Me      Me      8-Me    1   1                                         1b-7     n-Bu    Me      6-NMe2  1   1                                         ______________________________________                                    

The compounds of the invention may be administered by any method that produces contact of the active ingredient with the agent's site of action in the body of a mammal including but not limited to oral, intravenous, and intraparenteral. The compounds of the invention may be administered singly, or in combination with other compounds of the invention, other pharmaceutical compounds, such as chemotherapy compounds, or other therapies, such as radiation treatment The compounds are preferably administered with a pharmaceutically acceptable carrier selected on the basis of the selected route of administration and standard pharmaceutical practice.

The compounds of the invention are administered to mammals, preferably humans, in therapeutically effective amounts or concentrations which are effective to inhibit protein kinase C, or to inhibit tumor cell growth, inhibit inflammation of tissue, inhibit keratinocyte proliferation, inhibit oxidative burst from neutrophils or inhibit platelet aggregation The dosage administered in any particular instance will depend upon factors such as the pharmacodynamic characteristics of the particular compound of the invention, and its mode and route of administration; age, health, and weight of the recipient; nature and extent of symptoms; kind of concurrent treatment, frequency of treatment, and the effect desired It is contemplated that the daily dosage of the compounds will be in the range of from about 5 to about 400 mg per kg of body weight, preferably from about 10 to about 200 mg per kg body weight, and more preferably from about 10 to about 50 mg per kg per day, and preferably administered in divided doses 2 to 4 times a day or in sustained release form.

The compounds of the invention may be administered orally in solid dosage forms, such as capsules, tablets, and powders, or in liquid dosage forms, such as elixirs, syrups, and suspensions. They may also be administered parenterally in sterile liquid dosage forms.

The compounds of the invention may be formulated into dosage forms according to standard practices in the field of pharmaceutical preparations. See Remington's Pharmaceutical Sciences, A. Osol, Mack Publishing Company, Easton, Pa., a standard reference text in this field.

For example, the compounds of the invention may be mixed with powdered carriers, such as lactose, sucrose, mannitol, starch, cellulose derivatives, magnesium stearate, and stearic acid for insertion into gelatin capsules, or for forming into tablets. Both tablets and capsules may be manufactured as sustained release products for continuous release of medication over a period of hours. Compressed tablets can be sugar coated or film coated to mask any unpleasant taste and protect the tablet from the atmosphere or enteric coated for selective disintegration in the gastrointestinal tract.

Liquid dosage forms for oral administration may contain coloring and flavoring to increase patient acceptance, in addition to a pharmaceutically acceptable diluent such as water, buffer or saline solution.

For parenteral administration, the compounds of the invention may be mixed with a suitable carrier or diluent such as water, a oil, saline solution, aqueous dextrose (glucose), and related sugar solutions, and glycols such as propylene glycol or polyethylene glycols. Solutions for parenteral administration contain preferably a water soluble salt of the compound of the invention. Stabilizing agents, antioxidizing agents and preservatives may also be added. Suitable antioxidizing agents include sodium bisulfite, sodium sulfite, and ascorbic acid, citric acid and its salts, and sodium EDTA. Suitable preservatives include benzalkonium chloride, methyl- or propyl-paraben, and chlorbutanol.

EXAMPLES

The following are specific examples which are illustrative of the present invention and are not intended to limit the scope of the invention.

EXAMPLE 1 1,4-Bis-(3-Chloro-2-Hydroxypropylamino)-9, 10-Anthracenedione

Epichlorohydrin (84.5 mL, 1.08 mol) was added to a solution of 1,4 - diaminoanthraquinone (Aldrich Chemical Company, Milwaukee, Wis.) (10 g, 42 mmol) in glacial acetic acid (200 mL) at room temperature. The solution was stirred for 30 minutes at 90° C. and the solvent was removed under reduced pressure. The residue was purified by flash column chromatography (silica gel, CH₂ Cl₂ :MeOH/25:1) and recrystallized from CH₂ Cl₂ -Ether-Hexanes to give a pure blue solid of the title compound (12.46 g, 70%), mp 167°-169° C.: ¹ H NMR (CDCl₃) δ 3.21 (broad, 2H, OH), 3.5-3.6 (m, 6H, CHCH₂), 3.75 (d, J=3Hz, 4H, CH₂), 4.19 (broad, 2H, NH), 7.03 (d, J=3.2 Hz, 2H, ArH (2, 3)), 7.69 (m, 2H, ArH (6, 7)), 8.27 (m, 2H, ArH (5, 8)). Anal. Calcd for C₂₀ H₂₀ O₄ N₂ Cl₂ ×0.25 H₂ O: C, 56.15; H, 4.83; N, 6.55. Found: C, 56.18; H, 4.76; N, 6.29.

EXAMPLE 2 1-(3-Diethylamino-2-Hydroxypropylamino)-4-(Chloro-2-Hydroxypropylamino)-9, 10 Anthracenedione (Compound 1a-1 in Table 1)

Diethylamine (3.15 mL, 60.86 mmol) was added dropwise over 1.5 hours to a solution of 1,4-bis-(3-Chloro-2-hydroxypropylamino)-9, 10 anthracenedione (12.88 g, 30.43 mmol) the compound of Example 1, compound 2 in Schemes I and II. in ethanol (200 mL) under nitrogen atmosphere. The solution was stirred for 48 hours at reflux and the solvent was removed under reduced pressure. The residue was purified by flash column chromatography (silica gel, CH₂ Cl₂ :MeOH / 25:1) and recrystallized from CH₂ Cl₂ -ether-hexanes to give a blue solid of the title compound 1-(3-diethylamino-2-hydroxypropylamino)-4-(-chloro-2-hydroxypropylamino)-9, 10 anthracenedione which is compound 1a-1 in Table I (8.1 g, 60%), mp 165° C.: ¹ H NMR (CDCl₃) δ 1.10 (t, J=7Hz, 6H, CH₃) 2.63 (m, 4H, CH2), 2.74 (m, 2H, CH₂), 3.44 (m, 2H, CH₂), 3.56 (m, 1H, CH), 3.63 (m, 1H, CH), 3.73 (m, 2H, CH₂), 4.17 (broad, 1H, NH), 4.19 (broad, 1H, NH), 7.22 (s, 2H, ArH (2, 3)), 7.68 (m, 2H, ArH (6, 7)), 8.3 (m, 2H, ArH (5,8)). Anal. Calcd for C₂₄ H₃₀ O₄ N₃ Cl *1.25 H₂ O: C, 59.74; H, 6.69; N, 8.71. Found: C, 59.50; H, 6.27; N, 8.50.

EXAMPLE 3 1-(3-Diethylamino-2-Hydroxypropylamino)-4-(3-Chloro-2-Hydroxypropylamino)-9, 10-Anthracenedione Hydrochloride Salt (Compound 1a-1 in Table 1)

Concentrated HC1 (8 drops) was slowly added to a solution of 1-(3-diethylamino-2-hydroxypropylamino)-4-(3-chloro-2-hydroxypropylamino)-9, 10-anthracenedione (0.531 g, 2.36 mmol) in acetone-dichloromethane (50%, 15 mL). A color change from purple to red was observed. The solid was obtained by filtration, mp 106°-108° C., extremely hygroscopic. ¹ H NMR (D₂ O) δ 1.40 (t, J=7.3 Hz, 6H, CH₃), 2.90 (m, 4H, CH₂), 3.29 (m, 4H, CH₂), 3.38 (m, 3H, CH₂, CH), 3.73 (m, 3H, CH₂, CH), 3.92 (broad, 1H, NH), 4.15 (broad, 1H, NH), 6.23 (s, 2H, ArH (2, 3)), 7.26 (m, 2H, ArH (6, 7)), 7.32 (m, 2H, ArH (5, 8)). Anal. Calcd for C₂₄ H₃₀ ClN.sub. 3 O₄ 2HCl 1.5 H₂ O: C, 51.48; H, 6.30; N, 7.50. Found: C, 51.70; H, 6.35; N, 7.41.

EXAMPLE 4 1,4-Bis-(2, 3-Epoxypropylamino)-9, 10-Anthracenedione

Sodium hydroxide (3.5 g) was added to a solution of 1,4-bis-(3-chloro-2-hydroxypropylamino)- 9, 10-anthracenedione (8.3 g, 19.8 mmoles), the compound of Example 1, in MeOH (500 mL) at 60° C. The resulting blue solution was stirred at room temperature for 4 hours, and the solvent was removed under reduced pressure. The residual solid was then purified by flash column chromatography (silica gel, CH₂ Cl₂ : MeOH / 25:1). Recrystallization from CH₂ Cl₂ : hexanes yielded the title compound 1,4-bis-(2, 3-epoxypropylamino)-9, 10-anthracenedione which is compound 3 in Scheme 2 (6.2 g, 89.37%), mp 189°-190° C.: ¹ H NMR (CDCl₃) δ 2.74 (m, 1H, CH₂), 2.87 (m, 1H, CH₂), 3.26 (m, 1H, CH), 3.57 (m, 1H CH₂), 3.78 (m, 1H, CH₂), 7.32 (s, 2H, Ar (2 ,3 )), 7.71 (dd, J=3.2 Hz, 5.5 Hz, 2H, Ar (6, 7)), 8.34 (dd, J=3.2 Hz, 5.5 Hz, 2H, Ar (5, 8)), 10.76 (s, 2H, NH). Anal. Calcd for C₂₀ H₁₈ O₄ N₂ ×0.25 H₂ O: C, 67.66; H, 5.25; N, 7.93. Found: C, 67.72; H, 5.55; N, 7.54. IR: 3400, 3070, 2910, 1640, 1220, 900.

EXAMPLE 5 1-(3-Diethylamino-2-Hydroxypropylamino)-4-(2, 3-Epoxypropylamino)-9, 10-Anthracenedione (Compound 1b-1 of Table 1)

Potassium hydroxide (0.3 g, 5.36 mmole) was added to a solution of 1-(3-diethylamino-2-hydroxypropylamino)-4-(3-chloro-2-hydroxypropylamino)-9, 10-anthracenedione hydrochloride salt (1 g, 1.78 mmole), the compound of Example 3, in methanol. The mixture was stirred at room temperature for 48 hours. Solvent was removed under reduced pressure and the residue was purified by flash column chromatography (silica gel, chloroform with a methanol gradient up to a ratio of 10:1) to give the title product 1-(3-diethylamino-2-hydroxypropylamino)-4-(2, 3-epoxypropylamino)-9, 10-anthracenedione which is compound 1b-1 of Table 1 (391 mg, 52%), mp 98° C.: NMR (CDCl₃) δ 1.06 (t, J=7.1 Hz, 6H, CH₃), 2.62 (m, 7H, CH₂), 2.87 (m, 1H, CH₂), 3.27 (m, 1H, CH₂), 3.49 (m, 2H, CH₂), 3.59 (m, 1H CH₂), 3.77 (m, 1H, CH), 3.96 (m, 1H, CH), 7.35 (s, 2H, Ar (2, 3)), 7.71 (m, 2H, Ar (6, 7)), 8.35 (m, 2H, Ar (5, 8)), 10.80 (b, 1H, NH), 10.92 (b, 1H, NH); Anal. Calcd for C₂₄ H₂₉ N₃ O₄ : C, 68.1; H, 6.90; N, 9.92. Found: C, 67.86; H, 6.96; N, 9.85.

EXAMPLE 6 1-(3-Diethyl-2-Hydroxypropylamino)-4-(2, 3-Dihydroxypropylamino)-9, 10-Anthracenedione Hydrochloride Salt (HCl salt of compound 1C-1 of Table 1)

Para-toluenesulfonic acid (272 mg, 1.43 mmole) was added to a solution of 1-(3-diethylamino-2-hydroxypropylamino)-4-(2, 3-epoxypropylamino)-9, 10 anthracenedione (120 mg, 0.28 mmole), the compound of Example 5, in methanol-water (1:1, 20 mL). The mixture was stirred for 16 hours at room temperature. The solvent was removed under reduced pressure and the residue was treated with chloroform-water. The organic layer was dried over magnesium sulfate and, after the removal of solvent, the residue was purified by column chromatography (silica gel, CH₂ Cl₂ with an increasing methanol gradient to give the product as a free base. Hydrochloride gas was passed through a methanolic solution of the free base until a color change was noted. The title compound 1-(3-diethyl-2-hydroxypropylamino)-4-(2, 3-dihydroxypropylamino)-9, 10 anthracenedione hydrochloride salt was then isolated by filtration and was found to be extremely hygroscopic. NMR (CDCl₃) δ 1.06 (t, J=7.1 Hz, 6H, CH₃), 2.72-2.55 (m, 6H, CH₂), 3.19 (m, 4H, CH₂), 3.31 (b, 3H, OH), 3.81 (m, 2H, CH), 3.87 (b, 1H, OH), 3.92 (m, 2H, CH₂), 4.11 (b, 1H, OH), 6.65 (m, 2H, Ar (2, 3)), 7.52 (m, 2H, (6, 7)), 8.08 (m, 2H, (5, 8)), 10.73 (m, 2H, NH);

EXAMPLE 7 Protein Kinase C Inhibition

The protein kinase C (PKC) assay is designed to duplicated the in vivo conditions required for protein kinase C function. Therefore, pH, salt and cofactor concentrations are similar to physiologic levels. Histone H1 (lysine rich) is used in the assay as the phosphorylation acceptor protein because it is readily available and serves as a good substrate for protein kinase C. The enzyme is prepared from rat brain and is purified to apparent homogeneity as determined by a single band on silver stained SDS-polyacrylamide. Studies on the mechanism of regulation of protein kinase C by phospholipids, DAG and Ca⁺² have been hampered by the physical properties of the lipid cofactors. In the screening assay, phosphatidylserine (PS) and DAG are cosonicated to form unilamellar and multilamellar vesicles. The concentration of lipids in the assay are suboptimal to maximize the detection potential of the assay for inhibitors. Potential inhibitor compounds are added to the assay in dimethylsulfoxide at three concentrations to give final inhibitor concentrations of 4.3, 43 and 218 μM, respectively. The assay is started with the addition of enzyme and stopped after 10 min by the addition of 25% trichloroacetic acid (TCA) and 1.0 mg/ml bovine serum albumin (BSA). The radioactive histone product is retained and washed on glass fiber filters that allow the unreacted ³² P-ATP to pass through. The amount of phosphorylation is determined by the radioactivity measured in a scintillation counter. Controls are included in every assay to measure background activity in the absence of enzyme, activity in the absence of lipids and the maximum enzyme activity with saturating levels of the activator lipids. Assay components and concentrations are given in Table 3.

                  TABLE 3                                                          ______________________________________                                         Assay Component      Concentration                                             ______________________________________                                         Hepes pH 7.5         20      mM                                                MgCl.sub.2           20      mM                                                CaCl.sub.2           100     μM                                             EGTA                 95      μM                                             Histone H1           200     μg/ml                                          Phosphatidylserine   40      μg/ml                                          Diacylglycerol       1.8     μg/ml                                          Protein Kinase C     0.6     μg/ml                                          .sub.γ -.sup.32 P-ATP                                                                         20      μM                                             ______________________________________                                    

Results of the protein kinase C assay are shown in Table 4 in the column labeled protein kinase C. Results are shown as IC₅₀, which is the concentration of test compound needed to inhibit 50% of the protein kinase C activity as compared with levels of protein kinase C activity in controls. As shown in Table 4, all but one of the compounds tested was able to inhibit fifty per cent of protein kinase C activity at concentrations less than 200 μM. Compound 1b-1 (base) had the lowest IC₅₀ of 110 μM, whereas compound 1a-1 (HCl salt) had the highest IC₅₀ of the test compounds at 230 μM.

                  TABLE 4                                                          ______________________________________                                         IC.sub.50 (μM)                                                              Exp.              PKC    PKA                                                   ______________________________________                                         1a-1 (base)       180    n.e.                                                  1a-1 (HCl)        230    n.e.                                                  1a-2 (HCl)        160    n.e.                                                  1a-3 (HCl)        110    n.e.                                                  1c-1 (HCl)        180    n.e.                                                  1b-1 (base)       110    n.e.                                                  ______________________________________                                          (In Table 4, n.e. = no effect)                                           

EXAMPLE 8 cAMP Dependent Protein Kinase (PKA) Assay

Compounds found to be inhibitors of protein kinase C were also tested for inhibitory activity against cAMP dependent protein kinase (PKA). This enzyme, like protein kinase C, plays an important role in cell-cell communication and is activated by a second messenger, cAMP. Secondary screening against PKA is useful for ascertaining the selectivity of the compounds of the invention. The standard assay conditions are given in Table 5. The catalytic subunit of PKA (Sigma Chemical Company, St. Louis, Mo.) is mixed with buffer before addition of the inhibitor in dimethylsulfoxide (DMSO). The assay is started by the addition of ³² P-ATP and the reaction is allowed to proceed for 10 min before stopping with 25% trichloroacetic acid (TCA) and 1.0 mg/ml bovine serum albumin (BSA). The phosphorylated protein is isolated by filtration and the radioactivity is counted in a beta scintillation counter.

                  TABLE 5                                                          ______________________________________                                         Assay Components     Concentration                                             ______________________________________                                         Hepes pH 7.5         20      mM                                                Histone              200     μg/ml                                          Dithiothreitol       32      μg/ml                                          Protein Kinase       2.6     μg/ml                                          .sub.γ -.sup.32 -ATP                                                                          20      μM                                             ______________________________________                                    

Results of the PKA assay are shown in Table 4 (in Example 7) in the column labeled PKA. As shown in Table 4, the compounds of the invention that were tested had no effect on PKA. The tested compounds of the invention are selective for protein kinase c, and have no effect on cAMP dependent protein kinase. The compounds of the invention should thus have no effect on the metabolic pathways associated with stimulation of protein kinase by cAMP.

EXAMPLE 9 Human Tumor Growth Inhibition

MCF-7 a human breast tumor cell line, and MCF-7/ADR an adriamycin resistant line of MCF-7 cells were obtained from the National Cancer Institute, Frederick, Md. NHEK a human keratinocyte cell line was obtained from Clonetic Corp., San Diego, Ca. 8226 a human myeloma cell line, 8226/MT a Mitoxantrone resistant line of 8226 cells, and 8226 ADR an adriamycin resistant line of 8226 cells were obtained from Dr. Bill Dalton, Arizona Cancer Center, Tuscon, Ariz.

Human tumor cells are trypsinized (0.05% trypsin, GIBCO), counted with a hemacytometer and seeded at a concentration of 10,000 cells/well in a 96 well microtiter plate. After allowing cells to attach to the surface overnight, the culture medium is aspirated and replaced with 100 μl of fresh medium Test agents are diluted to determine dose response at 2×final concentration and added in quadruplicate at 100 μl/well to bring the total volume of each well to 200 μl. The microtiter plate is then incubated at 37° C. 5% CO₂ overnight (18-24 hrs) before ³ H-thymidine is added at a concentration of 0.5 μCi/well in 50 μl culture medium. The plate is incubated again for 4 hrs under the same conditions as above. Supernatant is then aspirated and 50 μl trypsin (0.05%, GIBCO) is added to each well. Cells are checked microscopically to determine detachment from surfaces, and plates are then harvested with a cell harvester (PHD, Cambridge Technology, Inc.) Filter papers corresponding to wells are placed in scintillation vials and counted to determine the amount of ³ H-thymidine incorporated by the cells. Test agent response is compared to a positive control of cell wells with culture media only to determine the IC₅₀. IC₅₀ is the concentration of test compound required to inhibit fifty per cent of the incorporation of ³ H-thymidine into proliferating cells not exposed to test agent. Uptake of ³ H-thymidine is a standard test for measuring the metabolism of cells. Cells which are actively proliferating take up ³ H-thymidine, whereas cells that are not proliferating take up ³ H-thymidine at much slower rates or not at all. Test agents that inhibit the uptake of ³ H-thymidine thus slow the growth of cells.

Results of these experiments are shown in Tables 6 and 7. As shown in Table 6, both compounds 1a-1 and 1b-1 were able to inhibit fifty per cent of ³ H-thymidine uptake at concentrations less than 1 μM (IC₅₀ =0.25 μM and 0.025 μM, respectively). The IC₅₀ of compound 1b-1 especially compares well with the IC₅₀ of adriamycin.

When compounds of the invention were tested with adriamycin resistant cell line MCF-7/ADR, the IC₅₀ of the test compounds increased to amounts from 0.06 to 16 μM, resulting in a resistance ratio of IC₅₀ for MCF-7/ADR cells to IC₅₀ for MCF-7 cells of from 1.9 to 2.4. In contrast, the IC₅₀ for MCF-7/ADR cells cultured with adriamycin was 4 μM, with a ratio of 200. The IC₅₀ for MCF-7/ADR cells cultured with Mitoxantrone was also 4 μM, but the ratio of IC₅₀ for MCF-7/ADR cells to IC₅₀ for MCF-7 cells was 800.

Similar results were obtained when the compounds were tested with cell lines 8226, 8226/MT (Mitoxantrone resistant) and 8226/ADR (adriamycin resistant). Compounds 1a-1 and 1b-1 were able to inhibit ³ H-thymidine uptake at very low concentrations. The IC₅₀ for compound 1a-1 was 1 μM. The IC₅₀ for compound 1b-1 was 0.06 μM. The IC₅₀ for the other compounds tested were 10.2 and 15 μM. When compounds 1a-1 and 1b-1 were tested with cell line 8226/MT the IC₅₀ was 0.24 and 0.008, respectively, with a ratio of IC₅₀ for 8226 cells to IC₅₀ for 8226/MT cells of 0.24 and 0.13 respectively. These results compared favorably with the results obtained from cells cultured with adriamycin or Mitoxantrone. The ratio of IC₅₀ for 8226/MT cells to IC₅₀ for 8226 cells for cells cultured with adriamycin was 1 μM.

The ratio of IC₅₀ for 8226/MT cells to IC₅₀ for 8226 cells for cells cultured with Mitoxantrone was 3.5.

Compounds tested with adriamycin resistant 8226 cells also showed a similar results. The test compound s were not cross-resistant with adriamycin as shown by the ratio of IC₅₀ for 8226/ADR cells to IC₅₀ for 8226 cells ranging from 0.08 μM to 1.4 μM for test compounds compared with resistance ratios of 11.4 μM and 6 μM for adriamycin and mitoxantrone, respectively.

These results show that the compounds of the invention are effective in inhibiting the proliferation of tumor cells and are not cross-resistant with adriamycin or mitoxantrone.

                  TABLE 6                                                          ______________________________________                                         Compound   MCF-7   MCF-7/ADR    Resistance Ratio                               ______________________________________                                         1a-1       0.25    0.5          2                                              1a-2       7.4     16           2.2                                            1a-3       7.4     14.1         1.9                                            1b-1       0.025   0.06         2.4                                            ADR        0.02    4            200                                            MT         0.005   4            800                                            ______________________________________                                    

                  TABLE 7                                                          ______________________________________                                         Com-                  Resistance      Resistance                               pound 8226   8226/MT  Ratio   8226/ADR                                                                               Ratio                                    ______________________________________                                         1a-1  1      0.24     0.24    0.08    0.08                                     1a-2  10.2                    14.1    1.38                                     1a-3  15                      16.3    1.08                                     1b-1  0.06   0.008    0.13    0.016   0.26                                     1c-1  18                      25      1.4                                      ADR   0.05   0.05     1       0.57    11.4                                     MT    0.03   0.105    3.5     0.18    6                                        ______________________________________                                    

EXAMPLE 10 Human Keratinocyte Inhibition

Proliferating keratinocytes (NHEK cells purchased from Clonetics, Inc. San Diego, Ca.) in second passage were grown in Keratinocyte Growth Medium (KGM) (Clonetics, Inc.) Cells were trypsinized with 0.025% trypsin (Clonetics), counted with a hemacytometer (Scientific Products), and seeded at a concentration of 2,500 cells/well in a 96 well microtiter plate. After allowing cells to attach to the surface overnight, the culture medium is aspirated and replaced with 100 μl of fresh KGM. Test agents were evaluated and IC₅₀ 's are determined according to the ³ H-thymidine incorporation procedures described as in Example 9.

The results of these experiments are shown in Table 8. These results indicate that compounds of the invention are active against human keratinocytes, and will be useful in treating topical inflammatory conditions such as psoriasis and other conditions where hyperproliferation of keratinocytes is a symptom.

                  TABLE 8                                                          ______________________________________                                         Compound      IC.sub.50 (μM)                                                ______________________________________                                         1a-1          0.16                                                             1b-1          0.04                                                             ______________________________________                                    

EXAMPLE 11 Neutrophil Superoxide Anion (O₂ -) Release Assay

Neutrophils were isolated form whole blood collected from human volunteers. All reagent materials were obtained from Sigma Chemical Company with the exception of isotonic saline (Travenol Lab., Inc. Deerfield, Ill.) and lymphocyte separation medium (Organon Teknika, Durham, N.C.).

Neutrophil Isolation

Whole blood was drawn and mixed with sodium heparin (final conc. 10 units/ml) to prevent clotting. An equal volume of dextran (3.0%) in isotonic saline was added, mixed, and allowed to settle for 30 min to bind red blood cells (RBC). The supernatant was removed, underlayered with lymphocyte separation medium and centrifuged for 40 min at 400×g in a centrifuge (Beckman GPR, Norcross, Ga.). The pellet was alternately resuspended in 0.2% and 1.6% NaCl to lyse RBCs before washing with Hank's Balanced Salt Solution (HBSS). The washed pellet was resuspended in 10 ml HBSS and placed on ice before counting on a hemacytometer.

Assay Procedure

The neutrophil cell concentration is adjusted to 2×10⁶ cells/ml with HBSS before adding 0.8 ml cells to 12×75 mm polypropylene test tubes (Fisher Scientific). Test agents are diluted to determine dose response and added at 10×final concentration at a volume of 0.1 ml/tube in duplicate. Then 10×concentrations of cytochrome C (15 mg/ml) with catalase (3000 units/ml) either alone or containing 25 ng/ml phorbol 12-myristate 13-acetate (PMA) are added at a volume of 0.1 ml/tube and incubated at 37° C. for 30 min before stopping the reaction by placing tubes on ice. Tubes are then centrifuged at 900×g for 10 min, 0.5 ml supernatant is removed and added to 0.5 ml H₂ O in a microcuvette. Optical density (OD) of cytochrome c is read in a spectrophotometer (Shimadzu) at 550 nm. The ΔOD of cytochrome c is obtained between PMA-stimulated and non-stimulated tubes, and the dose responses of the test agents are compared to the positive controls (which contain HBSS in place of test agents). PMA stimulates O₂ production which reduces cytochrome c. Reducing cytochrome c increases its absorbance, and the change in OD of cytochrome c is proportional to the amount of O₂ produced by PMA stimulation. Inhibition of the O₂ burst by test compounds of the invention is seen as a reduction in the change in optical density. Inhibition is expressed as IC₅₀ μM and is the amount of test compound that will inhibit fifty per cent of the PMA-stimulated respiratory outburst, i.e. O₂ production.

The tested compounds were able to inhibit O₂ production by PMA-stimulated neutrophils. As shown in Table 9, compound la-1(base) had an IC₅₀ greater than 6.25 μM. Compounds 1a-1 (HCl) and 1b-1 (base) had IC₅₀ of greater than 12.5 μM and 25 μM, respectively.

    ______________________________________                                         IC.sub.50 (μM)                                                              Exp.         Human Neutrophil                                                  ______________________________________                                         1a-1 (base)  >6.25                                                             1a-1 (HCl)   >12.5                                                             1b-1 (base)  >25                                                               ______________________________________                                     

We claim:
 1. A substituted anthraquinone having the formula ##STR4## wherein R₁ and R₂ are independently H, C₁ -C₁₀ alkyl, aryl, arylalkyl, alkylaryl;n and m are independently 1, 2, or 3; A is Halogen, OH, alkoxy, OCO(NR₃ R₄), S--C(NH₂)═NR₅, or when m=1, comprises an oxirane ring with the adjacent oxygen atom; R₃, R₄, and R₅ are independently H, alkyl, or aryl; X is H, OH, NR₆ R₇, Cl, Br, I, F, alkyl, aryl, alkoxy, aryloxy, COOR₈, or CONR₉ R₁₀ ; and R₆, R₇, R₈, R₉, and R₁₀ are independently H, lower alkyl, or aryl.
 2. The substituted anthraquinone of claim 1 whereinR₁ and R₂ independently are H or lower alkyl; n and m are independently 1 or 2; A is halogen, OCO(NR₃ R₄), SC(NH₂)═NR₅, or when m=1, comprises an oxirane ring with the adjacent oxygen atom; R₃, R₄, and R₅ are independently H or alkyl; and X is H, HO, Cl, Br, I, F, or alkoxy.
 3. The substituted anthraquinone of claim 2 whereinR₁ and R₂ independently are lower alkyl; m and n are 1; A is Cl, Br, OCO(NR₃ R₄), SC(NH₂)═NR₅, or when m=1, comprises an oxirane ring with the adjacent oxygen atom; R₃, R₄, and R₅ are H; and X is H or OH.
 4. A pharmaceutical composition for inhibiting protein kinase C comprising a substituted anthraquinone of claim 1 and a pharmaceutically acceptable carrier or diluent.
 5. A pharmaceutical composition for inhibiting protein kinase C comprising a substituted anthraquinone of claim 2 and a pharmaceutically acceptable carrier or diluent.
 6. A pharmaceutical composition for inhibiting protein kinase C comprising a substituted anthraquinone of claim 3 and a pharmaceutically acceptable carrier or diluent. 